The present invention relates to a sheet feeding apparatus used for an image forming apparatus such as a copying machine, a printer, a facsimile machine and a multi function machine having the functions thereof, and in particular, to a sheet feeding apparatus provided with a cleaning member to remove foreign objects such as paper dust adhered on a circumference surface of a sheet feeding roller.
As a foreign object removing device for an image forming apparatus, a fixed type cleaning member (flexible member such as brush, felt and PET sheet) in contact with a roller member to convey a recording sheet is used so as to remove the foreign object such as the paper dust. Also, a cleaning roller (brush or felt) in contact with the recording sheet conveyed is used to remove the foreign object such as the paper dust.
For example, in Patent Document 1, as the foreign object removing device, there is used the fixed type cleaning member such as a felt in contact with a conveyance roller to clean a surface of the recording sheet through the conveyance roller.
In Patent Document 2, a bush in contacted with a cleaning roller which cleans the recording sheet is used to clean the cleaning roller.
In Patent Document 3, a method, wherein the cleaning roller is in contact with the recording sheet to be conveyed is used.
In Patent Document 4, the conveyance roller is cleaned by contacting a rotating brush roller to the conveyance roller, and the brush roller is cleaned by contacting a rotation roller, and then the rotation roller is cleaned by contacting a plastic sheet.
[Patent document 1] Japanese Patent Non-Examined Publication No. 11-52641
[Patent document 2] Japanese Patent Non-Examined Publication No. 11-208918
[Patent document 3] Japanese Patent Non-Examined Publication No. 8-314344
[Patent document 4] Japanese Patent Non-Examined Publication No. 2004-224451
When a printed sheet, in particular, a sheet printed by offset printing passes through a sheet feeding device or a sheet conveyance device arranged in an image forming apparatus and a finishing apparatus, sprinkled flour, ink residue and coating agent on the sheet surface adhere on a circumference surface of the sheet feeding roller and the conveyance roller and deteriorate a conveyance capacity of the sheet feeding roller and the conveyance roller and then sheet feeding performance becomes unstable. Thus cleaning of the conveyance roller becomes necessary.
However, in the foreign object removing devices such as the fixed type cleaning member in contact with the aforesaid sheet feeding roller and the conveyance roller to remove the foreign object, the cleaning roller such as the rotation brush in contact with a transfer material to be conveyed to remove the foreign object, and the cleaning roller in contact with the transfer material to be conveyed to remove the foreign object and in the image forming apparatus utilizing the device thereof, there is a problem that removing of the foreign object such as the paper dust cannot be carried out in a stable condition for long period of time, then entering of the foreign object into a transferring area can not be reduced for a long period of time.
In a reverse roller type sheet feeding roller method, a rising fabric such as a moquette, and a flexible member such as an urethane foam or a PET sheet are imposed onto the roller to remove the foreign object such as the paper dust adhered on rotation rollers such as a pick roller and the feeding roller. However, in the rising fabric and the flexible member, since scraped foreign object cannot be separated from the roller, cleaning effect cannot be sustained and cleaning members and rollers need to be cleaned or replaced periodically.
In the image forming apparatus of Patent Document 1, there is a problem in durability that the foreign object such as the paper dust is accumulated in the cleaning member in short time, then the paper dust exceeding a capacity of cleaning is conveyed to the transferring area.
In the image forming apparatus of Patent Document 2, there was a problem that conveyance of a transfer material is unstable because the cleaning roller is configured to have a speed difference for the transfer material.
In the image forming apparatus of Patent Document 3, there was a problem in durability that when the foreign object such as the paper dust is accumulated on the surface of the cleaning roller, cleaning becomes not effective.
In the image forming apparatus of Patent Document 4, it is necessary to select a material of the conveyance roller rubber and the cleaning member appropriately, otherwise stable sheet conveyance performance and high efficiency of cleaning cannot be obtained.
Also, the pickup roller has to convey the sheet to the feeding roller without fail and a pressure the pickup roller presses the sheet has to be loaded appropriately. To apply the appropriate load stably, it is effective that the pressure is imposed by the weight of the pickup roller and its holder. In this case, there is occurred a problem that appropriate load cannot be applied because a cleaning mechanism of the pickup roller becomes large size.